A new experimental model has been found in this laboratory whereby Acute Hemorrhagic Pancreatitis with Fat Necrosis is induced in 100 percent of mice fed a choline-deficient diet supplemented with 0.5 percent dl-ethionine. The onset of the pancreatitis has been shown to be due to an endogenous activation of pancreatic zymogens, leading to the intraparenchymal formation of significant amounts of free elastase, chymotrypsin and trypsin. The model is used to investigate what factors arise during the onset of the process that are capable of causing the intraparenchymal activation of zymogens. The research proposed in this application is specifically addressed to study the importance, from this point of view, of alterations in the lipid compositions of the pancreas, as an index of alterations occuring in the membrane of the acinar cell organelles, especially the lysosomes. The role of lysosomal enzymes will also be investigated further.